Apparatus for removing coatings



June 8, 1937.

DE HART G. SCRANTOM APPARATUS FOR REMOVING COATINGS Filed April 4, 1935FIG.

FIG. 5.

a Q I r INVENTOR D. G- SCRANTOM ATTORNEY Patented June 8, 1937 UNITEDSTATES 2,118,407 APPARATUS FOR REMOVING COATINGS De Hart G. Scrantom,Maplewood, N. J., minor to Western Electric Company, Incorporated, NewYork, N. Y., a corporation of New York Application April 4, 1935, SerialNo. 14,634

8 Claims.

This invention relates to a method of and apparatus for removingcoatings and more particularly to a method of and apparatus forstripping insulation from predetermined portions of 5 insulatedelectrical conductors.

In the manufacture, alteration and repair of a great variety ofelectrical apparatus it is necessary to remove coatings of insulatingmaterial, such as molded compounds containing rubber,

10 asphalt, textile fibers of various-kinds, and other materials fromend portions of conductors or from restricted portions elsewhere forexample in order to make connections to theconductors.

An object of the present invention is to pro- 5 vide a simple andreliable method and apparatus for removing insulating or other coatingsfrom electrical conductors in a convenient and rapid manner.

One embodiment of the invention is in a method 20 and in an apparatusfor practicing the method which comprises the steps of and means forsubjecting a portion of an insulated electrical conductor from whichinsulation is to be removed to a freezing agent, preferably liquid air,until the coating but not the conductive element therein, is renderedbrittle, and then subjecting the frozen portion to mechanical shockorpressure to break oiT the coating.

Other objects and features of the invention 30 will appear from thefollowing detailed description of one embodiment thereof taken inconnection with the accompanying drawing in which the same referencenumerals are appended to identical parts in the several figures and inwhich 35 Fig. 1 is a vertical sectional view in perspective of a vacuumtank containing liquid air and a float therein for practicing one stepof the method of the invention;

Fig. 2 is a perspective view of an auxiliary 40 device;

Fig. 3 is a broken side view of a piece of insulated single strandconductor from which an end portion of insulation has been removed;

Fig. 4 is a similar view of a multi-conductor 45 cable, and

Fig. 5 shows a single strand insulated conductor with the insulationremoved from a non-terminal portion.

In the embodiment of the invention herein 5 disclosed there is provideda tank 20 preferably having hollow evacuated walls and bottom such asare customarily used in containers for liquid air. The tank is filled toa convenient depth with liquid air 2| or other sufficiently coldchilling agent. Solid carbon dioxid snow may be used, or liquidnitrogen, hydrogen or oxygen, or the like.

A disk-like float 22 of cork or other suitable material such as wood,sponge rubber, an artificial resin or the like floats on the surface ofthe 5 liquid air and has a vertically disposed aperture 24 of anyconvenient diameter. A flat annulus 23 of metal may be inset into thetop surface of the float around the aperture 24. A plurality, preferablythree or four, of vertical rods 25, each threaded at its upper end andheaded as at 21 at its lower, are disposed, preferably symmetrical- 1y,about the aperture, passing through appropriate bores in the float andannulus. A thumbnut 26 is mounted on the threaded upper end of each rod25 to adjustably regulate the distance of the heads 21 below the underface of the float. A stop 28 in the form of a suitably perforated disk,is supported on the heads 21.

Fig. 2 represents an auxiliary device comprising a block 30 of anysuitable hard material, wood, metal, stone or the like, and anupstanding metal blade 3| secured thereto and having a notch presentinga V-shaped cutting edge 32 at the upper end thereof.

To illustrate one mode of operation, let it be assumed that it isdesired to remove from an insulated conductor 40 (Fig. 3) that portion4| of the insulating coating shown in dotted lines to lay bare the outerright hand end of the single conductive strand 42, the strand beingeither a s ngle wire or a group of smaller wires which may be grouped orintertwisted or braided together. The thumbnuts 26 will be adjusteduntil the top face of the stop 28 stands at a distance below the surfaceof the liquid air equal to the length 4! of the insulation coating to beremoved.

The end of the conductor 40 is then plunged down vertically through theaperture 24 until the tip of the conductor 40 touches the stop 28, and40 is held in this position for a length of time sufficient to chill theinsulation to brittleness from without inwardly but not suflicient toalso render the metal strand 42 brittle. The period of time necessarywill vary with the nature and thickness 45 of the insulating coating andfor any L ven instance will have to be learned by experience. When thepredetermined period has elapsed the conductor is removed from theliquid air and the frozen portion 4i of its insulation is cracked off.In some instances this may be efficiently done by merely striking thefrozen end smartly on any hard smooth surface such as the top of theblock 30. Or the frozen end may; be laid on such a surface and tappedwith a hammer or other suitable tool. Or the frozen end may be crushedmore or less gently with a pair of pliers, or in a vise, or in any othersuitable device. Under such treatment, the frozen part ll of theinsulating coating cracks, chips or crumbles cleanly away from theinterior metallic strand, leaving the latter bare as desired.

In some instances the demarkation between the brittle frozen portion ofthe insulation and the elastic tough unfrozen part is sufllciently sharpthat the-end 43 of the insulation remaining is smooth and plane enoughfor practical purposes.

However, it may be desired in some instances to ensure neatness at thisface, and in such cases the conductor may be pressed and rolled gentlyin the knii'ev edged notch 32 to indent its outer surface slightly in aring demarking the portion II from the rest of the insulation, so thatthis annularindentation will stand at the surface of the liquid air whenthe freezing is done. It is not usually necessary that the knife makeany actual cut mon outer sheath of insulation. It may be desired insome" instances to remove a portion SI of the common vouter sheathwithout disturbing 'any of the individual sheaths 54 thereunder.

In such a case, a little experiment will show how long to subject theend cf the cable in any given case to the liquid air to render the outersheath brittle without destroying the toughness of the inner sheaths 54,and the frozen portion may be cracked of! without harming the innercoatings. Then if it be desired to bare a shorter length of the ends ofthe metallic conductors by removing portions 55 of the sheaths 54, thesemay be frozen and cracked oil! in a second operation.

If a portion SI of insulation not at an end of an insulated conductor 60is to be bared (Fig. 5), the whole may be doubled at the mid point ofthe portion to be removed, dipped and frozen to the line 6282, crackedoil, and the conductor straightened again.

Customary methods of removing portions of insulation are to whittle orscrape the sheath off manually with a knife, or to=burn itoif with aflame. In the one method it is difficult to avoid nicking or scoring themetal strand underneath or even in the case of a compound strand such aslitzendraht toavoid severing one or more of the component small wires.In the other method it is diflicult to control the burning within adefinite limit; and also particularly in the case of rubber compositionsfumes are produced which are not merely annoying but may even bepoisonous.

The method of the invention is rapid, convenient and accurate, neitherharming the metal nor producing fumes.

The embodiment of the invention herein disclosed is illustrative onlyand may be modified and departed from in many ways without departingfrom the spirit and scope of the invention as pointed out in and limitedonly by the appended claims.

What is claimed is:

u 1. An apparatus for chilling articles and comprising means to hold asupply of a chilling agent, and means responsive to the amount ofchilling agent present to control the extent to which an articleinserted therein to be partially exposed to the agent may be broughtinto contact there- 2. An apparatus for chilling articles and comprisingmeans to hold a supply of a chilling agent, and adjustable meansresponsive to the amount of chilling agent present to control the extentto which an article inserted therein to be partially exposed to theagent may be brought into contact therewith.

3. An apparatus for chilling articles and comprising means to hold asupply of liquid air, and means responsive to'the amount of liquid airpresent to control the extent to which an article inserted therein to bepartially exposed to the liquid air may be brought into contacttherewith.

4. An apparatus for chilling articles and comprising means to hold asupply of liquid air, and adjustable means responsive to the amount ofliquid air present to control the extent to which an article insertedtherein to be partially exposed to the liquid air may be brought intocontact therewith.

5. An apparatus for chilling articles and comprising a chamber to hold asupply of a chilling agent, and a stop supported therein by the chilling agent to limit the extent to which an article inserted therein to bepartially subjected to the agent may be inserted thereinto.

6. An apparatus for chilling articles and comprising a chamber to hold asupply of a chilling agent, and an adjustable stop supported therein bythe chilling agent to limit the extent to which an article insertedtherein to be partially subjected to the agent may be insertedthereinto.

'7. A chilling apparatus comprising a tank to hold a supply of aliquefied gas, a float therein, and a stop member carried by the floatto limit the extent to which an article to be partially subjected to theliquefled'gas may be inserted thereinto.

8. A chilling apparatus comprising a tank to hold a supply of aliquefied gas, a float therein, and anadjustable stop member carried bythe float to limit the extent to which an article to be partiallysubjected to the liquefied gas may be inserted thereinto.

DE HART G. SCRANTOM.

